Beiträge zur Chemie des Phosphors. 222. Pentaisopropyl-tridecaphosphan(5), P13i-Pr5– Struktur in Lösung und im Kristall

Contributions to the Chemistry of Phosphorus. 222. Pentaisopropyltridecaphosphane(5), P₁₃iPr₅ – Structure in Solution and in the Crystal In an earlier investigation [3] pentaisopropyltridecaphosphane(5) ( 1 ) had been obtained by reacting i-PrPCl₂, P₄ and magnesium and subsequently thermolysing the crude reaction product, but had been structurally characterized only incompletely. We have now corroborated the earlier postulated constitution by NMR spectroscopic studies and an X-ray structural analysis. Thus 1 is 3,4,7,10,11-pentaisopropyl-pentacyclo[7.4.0.0^2,6.0^5,13.0^8,12]tridecaphosphane. In solution two configurational isomers 1 a and 1 b exist in the relative abundance of about 2 : 1, which have the symmetry C₁ and C_s, respectively. When crystallizing pure 1 b precipitates, which at room temperature in solution is retransformed into the isomeric mixture 1 a , 1 b by inversion of the configuration. Any indications of an additional symmetric diastereomer have not been found. Obviously, in isomer 1 b the inversion barrier of the atom P⁷ is markedly higher than for the atoms of the two-atom bridges P³? P⁴ and P¹⁰? P¹¹, respectively.     

Strukturen und Molekül-Eigenschaften ladungsgestörter Moleküle. 52. Mitteilung. 2, 3-Diphenylchinoxalin-Radikalanionen in Lösung und im Kristall

Structures and Molecular Properties of Charge-Pertubed Molecules. 2, 3-Diphenylquinoxaline Radical Anions in Solution and in Crystals The Na⊕ and K⊕ radical-ion salts of 2, 3-diphenylquinoxaline seem to be (according to a structural database search) among the first ones of N-heterocyclic radical anions in crystals. The one-electron reduction in aprotic 1, 2-dimethoxyethan (DME) solution at metal mirrors and the crystallization under Ar have been preceded by cyclovoltammetric (CV) and ESR/ENDOR measurement. The first electron insertion at ?1.63 V proves to be reversible, whereas the irreversible second step, which is accompanied by an overcrossing of the CV line, can be rationalized by an ‘ECE-DISP’ mechanism via a dianion redox disproportionation. The ENDOR spectrum resolves four ¹H couplings and allows to simulate the ESR spectrum including the ¹⁴N hyperfine splittings. Both dark-blue single crystals of the radical ion salts $[2,3{\rm - diphenylquinoxaline}^{{.} \ominus} {\rm Met}^ \oplus ({\rm DME})]^.$ show unexpected similarities for Met⊕ = Na⊕, K⊕ despite the 36-pm difference in their ionic radii. The largest structural changes inflicted by the one-electron reduction of the N-heterocyclic molecule are observed in the vicinity of the N-centers bearing the highest effective nuclear charge. The DME-chelated metal cations coordinate at the N electron pairs and form Met⊕(DME)-bridged polymer chains of the radical anion, which are differently ondulated in the Na⊕ and K⊕ radical anion salts. The take-home lesson suggests that many more N-heterocyclic molecules might be analogously reduced under optimized conditions and isolated as single crystals.     

Die Struktur des Selentetrafluorid in Lösung

The Structure of Selenium Tetrafluoride in Solution The fluorine exchange in selenium tetrafluoride is suppressed at ?140°C in solution of methylfluoride. SeF₄ is a monomer species under these conditions.     

Bildung und Fällung von Bromocadmaten in Essigsäure als Lösungsmittel

Cadmium bromide reacts in anhydrous acetic acid solutions with acetyl bromide to form bromocadmates which can be precipitated as ammonium salts. By conductometric control and X-ray diffraction the phases (NH₄)(CdBr₃), (NH₄)₂ (CdBr₄) and (NH₄)₄(CdBr₆) have been found which decompose on heating as ordinary double salts to ammonium bromide and cadmium bromide.